There are many safety syringes developed particularly to prevent discarded syringes and/or cannulas from unexpectedly stabbing and therefore undesirably injuring and infecting other people, including nursing and cleaning persons. U.S. Pat. Nos. 5,562,627; 5,405,327; 5,569,203; 5,899,887; 5,395,346, etc., all disclose syringes having specially associated hubs and barrels, so that hubs and cannulas held thereto of used syringes can be pulled back into the barrels without the risk of unexpectedly stabbing other people.
However, all these safety syringes of prior art developed to improve conventional syringes have a common problem. That is, although the hubs of these safety syringes may be stably connected to the barrels and be pulled back into the latter after the syringes have been used, the hubs are not always connected to the barrels in an airtight relation. As it is well-known that, when such safety syringes are assembled in the manufacturing process thereof, the hubs and the barrels must first be associated with one another before the syringes are sterilized, so that the assembled syringes would not be contaminated after the sterilization due to contact of any part of the syringes. However, the assembled hubs and barrels are subject to stress deformation and thermal deformation during the sterilization under high temperature and such deformation would have adverse influence on the stable and airtight connection of the hubs to the barrels.
It is therefore tried by the inventor to develop a further improved safety syringe to eliminate the drawbacks existing in the safety syringes of prior art.
A primary object of the present invention is to provide a safety syringe with a needle sleeve that is particularly made to improve a conventional safety syringe with a retractable hub. The needle sleeve of the safety syringe of the present invention allows the syringe to be sterilized with the hub and the barrel thereof in a contacted but non-engaged state, so that no stress deformation of the syringe would occur to adversely affect the airtight connection of the hub to the barrel of the syringe after the sterilization.
Another object of the present invention is to provide a safety syringe with a needle sleeve, so that the needle sleeve firmly holds the cap, the hub, and the barrel together to, on the one hand, prevent the cannula connected to the hub and covered by the cap from contamination by externally contacting the cannula, and, on the other hand, enable easy assembling of the hub to the barrel of the safety syringe simply by depressing the cap. And, the cap can be then pulled forward again to bring the needle sleeve to together separate from the syringe to expose the cannula for injection.